Methods of manufacturing low-temperature polysilicon thin film and transistor

ABSTRACT

A method of manufacturing a low temperature polysilicon thin film, including the steps of: forming a buffer layer on a substrate; forming a silicon layer on the buffer layer; roughening a surface of the silicon layer to form an uneven surface as a recrystallization growth space; and annealing the silicon layer to form a polysilicon layer, and a partial silicon material of the polysilicon layer is formed on the recrystallization growth space.

BACKGROUND Technology Field

This disclosure relates to methods of manufacturing a silicon thin filmand a transistor, and more particularly to methods of manufacturing alow temperature polysilicon thin film and a transistor.

Description of Related Art

Flat panel displays have been widely used in various fields. The liquidcrystal display device has superior features including the thin body,low power consumption and radiationless feature, has been graduallyreplaced the conventional cathode ray tube display device, and isapplied to many kinds of electronic products, such as a mobile phone, aportable multimedia device, a notebook computer, a liquid crystaltelevision, a liquid crystal screen and the like.

The liquid crystal display device includes elements such as a displaypanel and the like. At present, an active matrix type liquid crystaldisplay panel is a general display panel, which includes an activematrix substrate, an opposing substrate, and a liquid crystal layerinterposed between the two substrates. The active matrix substrate has aplurality of row wires, column wires and pixels, the pixels have pixeldrive elements, and the pixel drive elements are connected to the rowwires and the column wires. A general pixel drive element is a thin filmtransistor, and the row wires and the column wires are usually metalwires.

Thin film transistors of an active matrix substrate may be divided intoconventional amorphous silicon thin film transistors and low temperaturepolysilicon thin film transistors having the better conductive capacity.The low temperature polysilicon process often employs the excimer laserannealing technology, that is, the excimer laser is used as a heatsource, and the laser beam irradiates the amorphous silicon thin film tomake the amorphous silicon recrystallize and transform into thepolysilicon structure. Because the whole process is completed below 600°C., the general glass substrate is applicable. However, the surface ofthe polysilicon layer tends to have protrusions using the laserannealing, and the sizes of the protrusions affect the currentproperties of the transistor. This results in different operatingproperties of the transistors on the panel, and results in a decrease inthe display quality.

SUMMARY

In view of the deficiencies of the prior art, the inventor has obtainedthis disclosure after the research and development have been made. Anobjective of this disclosure is to provide methods of manufacturing alow temperature polysilicon thin film and a transistor, which canimprove the protruding problem on the surface of the low temperaturepolysilicon thin film.

This disclosure provides a method of manufacturing a low temperaturepolysilicon thin film, comprising the steps of: forming a buffer layeron a substrate; forming a silicon layer on the buffer layer; rougheninga surface of the silicon layer to form an uneven surface as arecrystallization growth space; and annealing the silicon layer to forma polysilicon layer, and a partial silicon material of the polysiliconlayer is formed on the recrystallization growth space.

In one embodiment, the step of roughening the surface of the siliconlayer is to etch the surface of the silicon layer.

In one embodiment, a surface of the buffer layer includes a plurality ofpores, and a partial silicon material of the polysilicon layer is filledinto the pores.

In one embodiment, the step of forming the buffer layer on the substratecomprises: forming a first sub-buffer layer on the substrate; andforming a second sub-buffer layer on the first sub-buffer layer, whereina meticulous degree of the second sub-buffer layer is lower than ameticulous degree of the first sub-buffer layer.

In one embodiment, the first sub-buffer layer is a diffusion barrierlayer.

In one embodiment, the method further comprises a step of: rougheningthe buffer layer to form the pores on the surface of the buffer layerbefore forming the silicon layer on the buffer layer.

In one embodiment, the method further comprises steps of: providing amask before the step of annealing the silicon layer to form thepolysilicon layer; and transferring a pattern from the mask to thesilicon layer, wherein the pattern is left with a recrystallizationgrowth space.

In one embodiment, a portion of the transferred pattern on the siliconlayer functions as a trench area, and the recrystallization growth spaceis located on a lateral side of the portion.

In one embodiment, the annealing is laser annealing.

This disclosure provides a method of manufacturing a low temperaturepolysilicon thin film transistor, comprising: the steps of the method ofmanufacturing the low temperature polysilicon thin film as mentionedabove; forming a gate insulating layer on the polysilicon layer; forminga gate on the gate insulating layer; and forming a source electrode anda drain electrode, wherein the source electrode and the drain electrodeare electrically connected to the polysilicon layer.

In summary, because the methods of manufacturing the low temperaturepolysilicon thin film and the transistor of this disclosure provide theamorphous silicon with the recrystallization growth space, the squeezebetween the crystals can be eased in the amorphous siliconrecrystallization process, and thus the sizes of the protrusions of thesurface of the polysilicon layer are significantly smaller. In thepreferred case, the aspect ratio of the protrusions is smaller than 0.3and even smaller than 0.2. Thus, the protruding problem on the surfaceof the low temperature polysilicon thin film can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will become more fully understood from the detaileddescription and accompanying drawings, which are given for illustrationonly, and thus are not limitative of the present disclosure, andwherein:

FIGS. 1A to 1C are schematic views showing an embodiment of a method ofmanufacturing a low temperature polysilicon thin film of thisdisclosure.

FIG. 1D is a schematic view showing an embodiment of a method ofmanufacturing a low temperature polysilicon thin film transistor of thisdisclosure.

FIGS. 2A to 2C are schematic views showing an embodiment of a method ofmanufacturing a low temperature polysilicon thin film of thisdisclosure.

FIGS. 3A to 3D are schematic views showing an embodiment of a method ofmanufacturing a low temperature polysilicon thin film of thisdisclosure.

FIGS. 4A to 4E are schematic views showing an embodiment of a method ofmanufacturing a low temperature polysilicon thin film of thisdisclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

Specific structures and function details disclosed herein are only forthe illustrative purpose for describing the exemplary embodiment of thisdisclosure. However, this disclosure can be specifically implementedthrough many replacements, and should not be explained as beingrestricted to only the embodiment disclosed herein.

In the description of this disclosure, it is to be understood that theterms “center”, “transversal”, “up”, “down”, “left”, “right”,“vertical”, “horizontal”, “top”, “bottom”, “inside” and “outside”indicating the orientation or position relationships are the orientationor position relationships based on the drawing, are only provided forthe purposes of describing this disclosure and simplifying thedescription, but do not indicate or imply that the directed devices orelements must have the specific orientations or be constructed andoperated in the specific orientations, and thus cannot be understood asthe restriction to this disclosure. In addition, the terms “first”, and“second” are used for the illustrative purpose only and cannot beunderstood as indicating or implying the relative importance orimplicitly specifying the number of indicated technical features.Therefore, the features restricted by “first” and “second” may expresslyor implicitly comprise one or a plurality of ones of the features. Inthe description of this disclosure, unless otherwise described, themeaning of “a plurality of” comprises two or more than two. In addition,the terms “comprises” and any modification thereof intend to cover thenon-exclusive inclusions.

In the description of this disclosure, it needs to be described that,unless otherwise expressly stated and limited, the terms “mount”, “link”and “connect” should be broadly understood. For example, they may be thefixed connection, may be the detachable connection or may be theintegral connection; may be the mechanical connection or may also be theelectrical connection; or may be the direct connection, may be theindirect connection through a middle medium or may be the innercommunication between two elements. It will be apparent to those skilledin the art that the specific meanings of the above terms in thisapplication may be understood according to the specific conditions.

The terms used herein are for the purpose of describing only specificembodiments and are not intended to limit the exemplary embodiments.Unless the contexts clearly indicate otherwise, the singular form “one”,“a” and “an” used here further intend to include plural forms. It shouldalso be understood that the terms “comprising” and/or “including” areused herein to describe the features to describe the presence of statedfeatures, integers, steps, operations, units and/or elements withoutexcluding the presence or addition of one or more other features,integers, steps, operations, units, elements, and/or combinationsthereof.

This disclosure will be further described below with reference to theaccompanying drawings and preferred embodiments.

FIGS. 1A to 1C are schematic views showing an embodiment of a method ofmanufacturing a low temperature polysilicon thin film of thisdisclosure. As shown in FIG. 1A, a method of manufacturing a lowtemperature polysilicon thin film firstly provides a substrate 11, andthe substrate 11 is, for example, a glass substrate. Then, a bufferlayer 12 is formed on the substrate 11. A surface of the buffer layer 12includes a plurality of pores, and the pores may function as the spacefor subsequent recrystallization of a silicon layer.

In addition, before forming the silicon layer on the buffer layer 12,the manufacturing method may further include a step of roughening thebuffer layer 12 to form pores on the surface of the buffer layer 12,wherein the aperture is smaller than 20 nm, for example. The roughenedsurface is an uneven surface.

As shown in FIG. 1B, a silicon layer 13 is formed on the buffer layer12. At this time, most of the silicon layer 13 is formed on the surfaceof the buffer layer 12, and the pores of the buffer layer 12 still havethe space not filled with the material of the silicon layer 13. Thesilicon layer 13 may be deposited on the buffer layer 12 usingconventional methods, and the material of the silicon layer 13 is anamorphous silicon.

As shown in FIG. 1C, after the amorphous silicon layer 13 is formed, theannealing is performed on the silicon layer 13 to form a polysiliconlayer 14 with a partial silicon material 140 of the polysilicon layer 14being filled into the pores 120.

The annealing is, for example, laser annealing, the annealing processtemperature is below 600 degrees Celsius, and the polysilicon thin filmobtained using this process may be called as the low temperaturepolysilicon (referred to as LTPS). Compared with the process temperatureup to 1000 degrees Celsius of the early polysilicon thin film, theprocess temperature of the low temperature polysilicon is lower.Therefore, the material of the substrate is less restricted. Forexample, a glass substrate may be used as the substrate 11.

The manufacture of the polysilicon layer 14 converts the originalamorphous silicon layer into a polysilicon layer by the annealingprocess, such as the laser crystallization or the excimer laserannealing (referred to as ELA) and the like. In the annealing process,amorphous silicon in the silicon layer 13 is melted and thenrecrystallized and rearranged to become polysilicon and thus to form thepolysilicon layer 14, a plurality of protrusions are formed on thesurface of the polysilicon layer 14, and the protrusions may be formedon the upper surface or the lower surface of the polysilicon layer 14.

As the amorphous silicon is recrystallized, a portion of the amorphoussilicon firstly functions as the recrystallized seeds, and then growsinto larger crystals, and these crystals continuously grow and arecombined to form the larger crystals. However, in the combining process,because the stresses of the crystals interact with one another, aportion of the crystals is pushed onto the surface of the polysiliconlayer 14 to form protrusions.

Since the buffer layer 12 leaves the pores 120 for the recrystallizationprotrusions, at least the protrusions 140 on the lower surface of thepolysilicon layer 14 may be filled into the pores 120. The pore 120 alsoconstrains the size and the shape of the protrusion 140 to prevent theprotrusion from getting oversized. Although protrusions (not shown) arealso formed on the upper surface of the polysilicon layer 14, since theportion of the protrusions is changed to the lower surface of thepolysilicon layer 14, the protruding situations on the upper surface areimproved. The aspect ratio of the protrusions of the polysilicon layerof the conventional process is about 0.45, and compared with theconventional process, the aspect ratio of the protrusions of thepolysilicon layer 14 can be reduced to be smaller than 0.3, and can evenbe reduced to be smaller than 0.2. Although there are protrusions on theupper and lower surfaces of the polysilicon layer 14, the aspect ratiosof the protrusions are not too large to affect the performance ofelements.

FIG. 1D is a schematic view showing an embodiment of a method ofmanufacturing a low temperature polysilicon thin film transistor of thisdisclosure. As shown in FIG. 1D, after forming the polysilicon layer 14on the substrate 11 as shown in FIG. 1C, the subsequent process isperformed to form a thin film transistor. The method of manufacturingthe low temperature polysilicon thin film transistor includes steps of:forming a gate insulating layer 15 on the polysilicon layer 14; andforming a gate 16 on the gate insulating layer 15; and forming a sourceelectrode 18 and a drain electrode 19, wherein the source electrode andthe drain electrode are electrically connected to the polysilicon layer.

For example, the low temperature polysilicon thin film transistorincludes the polysilicon layer 14, the gate insulating layer 15, thegate 16, a dielectric layer 17, the source electrode 18 and the drainelectrode 19. The polysilicon layer 14 is firstly patterned and thepatterned polysilicon layer 14 includes three areas including a source141, a drain 143 and a trench area 142, and the trench area 142 islocated between the source 141 and the drain 143. Then, the gateinsulating layer 15 is formed above the patterned polysilicon layer 14and the substrate 11, wherein the material of the gate insulating layer15 is, for example, silicon oxide or silicon nitride. Next, the gate 16is formed above the gate insulating layer 15 and the trench area 142.Then, a dielectric layer 17 is formed on the gate 16 and the gateinsulating layer 15, the dielectric layer 17 and the gate insulatinglayer 15 are patterned to form through holes, and the through holes mayexpose the source 141 and the drain 143. Then, the source electrode 18and the drain electrode 19 are formed on the surface of the dielectriclayer 17 and the through holes, the source electrode 18 passes throughthe through hole to contact the source 141, and the drain electrode 19passes through the through hole to contact the drain 143. Therefore, thesource electrode 18 and the drain electrode 19 are electricallyconnected to the source 141 and the drain 143 of the polysilicon layer14, respectively.

In addition, the low temperature polysilicon thin film transistor is notlimited to the use in a liquid crystal display panel or an organic lightemitter diode panel.

In addition, the substrate 11 may be composed of glass, quartz, orsimilar materials. The buffer layer 12 may be composed of materials suchas SiN_(x), SiO_(x) or SiO_(x)N_(y) and the like.

FIGS. 2A to 2C are schematic views showing an embodiment of a method ofmanufacturing a low temperature polysilicon thin film of thisdisclosure. As shown in FIG. 2A, a method of manufacturing a lowtemperature polysilicon thin film firstly provides a substrate 21, andthe substrate 21 is, for example, a glass substrate. Then, a bufferlayer 22 is formed on the substrate 21. A buffer layer 22 may be amulti-layer structure. In this embodiment, two layers are taken as anexample, but the number of layers is not limited to two, and more layersmay be provided.

The buffer layer 22 includes a first sub-buffer layer 221 and a secondsub-buffer layer 222. The step of forming the buffer layer 22 includes:forming the first sub-buffer layer 221 on a substrate 21, and thenforming the second sub-buffer layer 222 on the first sub-buffer layer221.

These sub-buffer layers may have different meticulous degrees, theuppermost sub-buffer layer in the buffer layer 22 may have a lowermeticulous degree, thereby forming the pores on the upper surface of theuppermost sub-buffer layer to function as the space required by therecrystallization of the silicon layer. For example, the meticulousdegree of the second sub-buffer layer 222 is lower than that of thefirst sub-buffer layer 221. Therefore, the upper surface the secondsub-buffer layer 222 includes a plurality of pores 220, and the pores220 may function as the space for subsequent recrystallization of thesilicon layer.

In addition, before forming the silicon layer on the buffer layer, themanufacturing method may roughen the second sub-buffer layer 222 to formpores on the surface of the buffer layer, wherein the aperture issmaller than 20 nm, for example. The roughened surface is an unevensurface.

Roughening may include etching, etching may be dry etching or wetetching, the process parameters of the dry etching include frequency,pneumatic, ion density, etch time and the like, and the processparameters of the wet etching include the solution concentration, etchtime, reaction temperature, stirring of the solution and the like. Theetched surface may have different roughnesses by adjusting the etchparameters.

The mask pattern transfer is not needed in the process of theroughening, the photoresist needs not to be disposed on the bufferlayer, and the mask and exposure are also not needed.

The first sub-buffer layer is a diffusion barrier layer. Becauseimpurities in the substrate 21 may be diffused to other layers in theannealing process, a diffusion barrier layer may block at least aportion of the impurities to prevent the excessive impurities fromdiffusing to the silicon layer. The first sub-buffer layer has a highermeticulous degree than the second sub-buffer layer to have the betterdiffusion barrier effect.

In addition, before the second sub-buffer layer 222 is formed, the firstsub-buffer layer 221 may be roughened by using the manufacturing methodto have the better diffusion barrier effect. The roughened surface is anuneven surface.

As shown in FIG. 2B, a silicon layer 23 is formed on the secondsub-buffer layer 222 of the buffer layer 22. At this time, most of thesilicon layer 23 is formed on the surface of the second sub-buffer layer222, and the pores of the buffer layer 12 still have the space notfilled with the material of the silicon layer 23. The silicon layer 23may be deposited on the second sub-buffer layer 222 using conventionalmethods, and the material of the silicon layer 23 is an amorphoussilicon.

As shown in FIG. 2C, after the amorphous silicon layer 23 is formed, theannealing is performed on the silicon layer 23 to form a polysiliconlayer 24 with a partial silicon material 240 of the polysilicon layer 24being filled into the pores 220 of the second sub-buffer layer 222.Because the formation and the structure of a polysilicon layer 24 aresimilar to the polysilicon layer 14, detailed descriptions thereof willbe omitted.

After forming the polysilicon layer 24, the subsequent process may alsobe performed, as shown in FIG. 1D, to form the thin film transistor. Themethod of manufacturing a transistor may refer to the relevantdescription of FIG. 1D, and detailed descriptions thereof will beomitted.

In addition, the substrate 21 may be composed of glass, quartz, orsimilar materials. The sub-layer of the buffer layer 22 may be composedof materials such as SiN_(x), SiO_(x) or SiO_(x)N_(y) and the like.

In addition, in FIGS. 1A and 2A, the manufacturing method of the lowtemperature polysilicon thin film may further include: rougheningsurfaces of silicon layers 13 and 23 to form uneven surfaces functioningas a recrystallization growth space, for example, the surface roughnessof the roughened surface ranges from 5 nm to 30 nm. Partial siliconmaterials of the polysilicon layers 14 and 24 are formed into therecrystallization growth space. The step of roughening the surfaces ofthe silicon layers 13 and 23 is, for example, etching the surfaces ofthe silicon layers 13 and 23. Due to the provision of morerecrystallization growth spaces, the squeeze between the crystals in therecrystallization process can be relieved and the size of theprotrusions on the surfaces of the polysilicon layers 14 and 24 can besignificantly reduced.

Roughening may include etching, etching may be dry etching or wetetching, the process parameters of the dry etching include frequency,pneumatic, ion density, etch time and the like, and the processparameters of the wet etching include the solution concentration, etchtime, reaction temperature, stirring of the solution and the like. Theetched surface may have different roughnesses by adjusting the etchparameters.

The mask pattern transfer is not needed in the process of theroughening, the photoresist needs not to be disposed on the bufferlayer, and the mask and exposure are also not needed.

In addition, in FIGS. 1B and 2B, the manufacturing method of the lowtemperature polysilicon thin film may further include: providing a maskbefore the step of annealing the silicon layer to form the polysiliconlayer; and transferring a pattern from the mask to the silicon layer,wherein the pattern is left with recrystallization growth space. Therecrystallization growth space is located on the lateral side of thepattern. Due to the provision of more recrystallization growth spaces,the squeeze between the crystals in the recrystallization process can berelieved and the size of the protrusions on the surfaces of thepolysilicon layers 14 and 24 can be significantly reduced.

The pattern on the silicon layer is transferred through a mask patterntransfer process. For example, an entire layer of photoresist is firstlydeposited on an unpatterned silicon layer, then the photoresist isexposed by the mask, and the mask pattern is transferred to thephotoresist firstly. Then, the etching process is used to etch thesilicon layer, which is not protected by the photoresist, so that themask pattern is transferred to the silicon layer.

In addition, a portion of the transferred pattern on the silicon layerfunctions as a trench area, and the recrystallization growth space isleft on the lateral side of the portion. For example, the mask patternis used to define positions of the source, the drain, the trench areaand the recrystallization growth space on the silicon layer. After themask pattern is transferred to the silicon layer, if the silicon layeris viewed from the top of the substrate, the trench area is flatlylocated between the source and the drain, the recrystallization growthspace is located on the lateral side of the trench area of the siliconlayer, and even the recrystallization growth space may be located on thelateral sides of the source and the drain of the silicon layer at thesame time.

In addition, in order to leave more recrystallization growth spaces, thelateral side surface may also be roughened by etching in the maskpattern transfer process to form more uneven surfaces functioning as arecrystallization growth space, for example, the surface roughness ofthe roughened surface ranges from 5 nm to 30 nm.

In addition, in FIGS. 1B and 2B, the manufacturing method of the lowtemperature polysilicon thin film may further include: forming a traplayer on the silicon layers 13 and 23 before the silicon layers 13 and23 are annealed to form the polysilicon layers 14 and 24. Because theimpurities of the substrates 11 and 21 may diffuse when being annealed,the trap layer may be provided to trap these impurities and to preventthe impurities form accumulating on the polysilicon layers 14 and 24.The material of the trap layer is, for example, the material such asSiN_(x), SiO_(x) or SiO_(x)N_(y) or the like. For example, the traplayer may be achieved by adjusting the process parameters. For example,the low-density SiO_(x) film layer may be formed by adjusting the ratioof reactants SiH₄ to N₂O or the ratio of reactants TEOS to O₂ or O₃. Ingeneral, the proportion of SiH₄ is larger, the porous nature of theSiO_(x) film layer is increasing; and if the proportion of gas getssmaller, the density of the SiO_(x) film layer gets smaller.

In summary, in the method of manufacturing the low temperaturepolysilicon thin film and the transistor, due to the provision of theamorphous silicon with the recrystallization growth space, the squeezebetween the crystals can be eased in the amorphous siliconrecrystallization process, and thus the sizes of the protrusions of thesurface of the polysilicon layer are significantly smaller. In thepreferred case, the aspect ratio of the protrusions is smaller than 0.3and even smaller than 0.2.

In addition, because the aspect ratios of the protrusions of the surfaceof the polysilicon layer are smaller than 0.3, the properties of theelements may be more consistent. When such a low temperature polysiliconthin film transistor is employed as a switch or driver of a displaypanel, the color uniformity of the display panel can be better.

FIGS. 3A to 3D are schematic views showing an embodiment of a method ofmanufacturing a low temperature polysilicon thin film of thisdisclosure. As shown in FIG. 3A, the manufacturing method provides asubstrate 31, and the substrate 31 is, for example, a glass substrate.Then, a buffer layer 32 is formed on the substrate 31.

As shown in FIG. 3B, the manufacturing method includes rougheningsurfaces of the silicon layer 33 to form uneven surfaces functioning asa recrystallization growth space, for example, the surface roughness ofthe roughened surface ranges from 5 nm to 30 nm. Roughening the surfacesof the silicon layer 33 is, for example, etching the surfaces of thesilicon layer 33. The silicon layer 33 may be deposited on the bufferlayer 32 using conventional methods, and the material of the siliconlayer 33 is an amorphous silicon.

As shown in FIG. 3C, a silicon layer 33 is annealed by the manufacturingmethod to form a polysilicon layer 34, and a partial silicon material ofthe polysilicon layer 34 is formed on the recrystallization growthspace.

The annealing is, for example, laser annealing. The relevantdescriptions of the annealing and recrystallization of amorphous siliconmay refer to the relevant contents of FIG. 1C, and detailed descriptionsthereof will be omitted.

Because the silicon layer 33 itself retains the recrystallization growthspace for the recrystallization protrusions, at least the protrusions onthe upper surface of the polysilicon layer 34 may be filled into therecrystallization growth space. The aspect ratio of the protrusions ofthe polysilicon layer of the conventional process is about 0.45, andcompared with the conventional process, the aspect ratio of theprotrusions of the polysilicon layer 34 can be reduced to be smallerthan 0.3, and can even be reduced to be smaller than 0.2 to alleviatethe influence of the protrusions on the element performance.

After forming the polysilicon layer 34, the subsequent process may alsobe performed, as shown in FIG. 1D, to form the thin film transistor. Themethod of manufacturing a transistor may refer to the relevantdescription of FIG. 1D, and detailed descriptions thereof will beomitted.

In addition, the buffer layer 32 may also employ the implementationmethod of FIGS. 1A and 2A.

For example, the buffer layer 32 may also employ the implementationmethod of FIG. 1A. The surface of the buffer layer 32 includes aplurality of pores, and the pores may function as the space forsubsequent recrystallization of the silicon layer, and a partial siliconmaterial of the annealed polysilicon layer is filled into the pores. Forexample, after forming the silicon layer 33 on the buffer layer 32, themanufacturing method may further include roughening the buffer layer 32to form the pores on the surface of the buffer layer 32. The relevantimplementation method may refer to the relevant description of the FIG.1A, and detailed descriptions thereof will be omitted.

The buffer layer 32 may also employ the implementation method of theFIG. 2A. The step of forming the buffer layer 32 includes: forming afirst sub-buffer layer on the substrate 31; and forming a secondsub-buffer layer on the first sub-buffer layer, wherein the meticulousdegree of the second sub-buffer layer is lower than that of the firstsub-buffer layer. The first sub-buffer layer may be a diffusion barrierlayer. The relevant implementation method may refer to the relevantdescription of the FIG. 2A, and detailed descriptions thereof will beomitted.

In addition, in FIG. 3B, the manufacturing method of the low temperaturepolysilicon thin film may further include: providing a mask before thestep of annealing the silicon layer to form the polysilicon layer; andtransferring a pattern from the mask to the silicon layer, wherein thepattern is left with recrystallization growth space. Therecrystallization growth space is located on the lateral side of thepattern. Due to the provision of more recrystallization growth spaces,the squeeze between the crystals in the recrystallization process can berelieved and the size of the protrusions on the surfaces of thepolysilicon layer 34 can be significantly reduced.

In addition, in FIG. 3B, the manufacturing method of the low temperaturepolysilicon thin film may further include: forming a trap layer on thesilicon layer 33 before the silicon layer 33 is annealed to form thepolysilicon layer 34. Because the impurities of the substrate 31 maydiffuse when being annealed, the trap layer may be provided to trapthese impurities and to prevent the impurities form accumulating on thepolysilicon layer 34.

In summary, in the method of manufacturing the low temperaturepolysilicon thin film and the transistor, due to the provision of theamorphous silicon with the recrystallization growth space, the squeezebetween the crystals can be eased in the amorphous siliconrecrystallization process, and thus the sizes of the protrusions of thesurface of the polysilicon layer are significantly smaller. In thepreferred case, the aspect ratio of the protrusions is smaller than 0.3and even smaller than 0.2.

FIGS. 4A to 4E are schematic views showing an embodiment of a method ofmanufacturing a low temperature polysilicon thin film of thisdisclosure. As shown in FIG. 4A, the manufacturing method provides asubstrate 41, and the substrate 41 is, for example, a glass substrate.Then, a buffer layer 42 is formed on the substrate 41.

FIG. 4B is a schematic side view showing the low temperature polysiliconthin film, and FIG. 4C is a schematic top view of FIG. 4B. As shown inFIG. 4B, the manufacturing method includes the step of forming a siliconlayer 43 on a buffer layer 42, the silicon layer 43 may be deposited onthe buffer layer 42 using conventional methods, and the material of thesilicon layer 43 is an amorphous silicon. As shown in FIG. 4C, themanufacturing method includes: providing a mask; and transferring apattern from the mask to the silicon layer 43. The pattern is left witha recrystallization growth space, and the recrystallization growth spaceis located on the lateral side of the pattern. If the silicon layer 43is viewed from the top of a substrate 41, the buffer layer 42 is seenbecause the recrystallization growth space is located on the lateralside of the pattern of the silicon layer 43. The recess above the bufferlayer 42 and the lateral side of the pattern on the silicon layer 43form the recrystallization growth space.

For example, the mask pattern is used to define positions of the source,the drain, the trench area and the recrystallization growth space on thesilicon layer 43. After the mask pattern is transferred to the siliconlayer 43, if the silicon layer 43 is viewed from the top of thesubstrate 41, the trench area is flatly located between the source andthe drain, the recrystallization growth space is located on the lateralside of the trench area of the silicon layer 43, and even therecrystallization growth space may be located on the lateral sides ofthe source and the drain of the silicon layer 43 at the same time.

In addition, the surface of the silicon layer 43 may be roughened toform uneven surfaces functioning as a recrystallization growth space.Roughening the surfaces of the silicon layer 43 is, for example, etchingthe surfaces of the silicon layer 43. For example, the surface roughnessof the roughened surface ranges from 5 nm to 30 nm. Thus, the uppersurface and the side surface of the silicon layer 43 are left with therecrystallization growth space.

FIG. 4D is a schematic side view showing the low temperature polysiliconthin film, and FIG. 4D is a schematic top view of FIG. 4C. As shown inFIG. 4D, a silicon layer 43 is annealed by the manufacturing method toform a polysilicon layer 44, and a partial silicon material of thepolysilicon layer 44 is formed on the recrystallization growth space.Thus, due to the provision of more recrystallization growth spaces, thesqueeze between the crystals in the recrystallization process can berelieved and the size of the protrusions on the surfaces of thepolysilicon layer 44 can be significantly reduced.

The annealing is, for example, laser annealing. The relevantdescriptions of the annealing and recrystallization of amorphous siliconmay refer to the relevant contents of FIG. 1C or FIG. 2C, and detaileddescriptions thereof will be omitted.

Because the silicon layer 43 itself retains the recrystallization growthspace for the recrystallization protrusions, thus, as shown in FIG. 4E,at least the protrusions on the upper surface of the polysilicon layer44 may be filled into the recrystallization growth space. The aspectratio of the protrusions of the polysilicon layer of the conventionalprocess is about 0.45, and compared with the conventional process, theaspect ratio of the protrusions of the polysilicon layer 44 can bereduced to be smaller than 0.3, and can even be reduced to be smallerthan 0.2 to alleviate the influence of the protrusions on the elementperformance.

After forming the polysilicon layer 44, the subsequent process may alsobe performed, as shown in FIG. 1D, to form the thin film transistor. Themethod of manufacturing a transistor may refer to the relevantdescription of FIG. 1D, and detailed descriptions thereof will beomitted.

In addition, the buffer layer 42 may also employ the implementationmethod of FIGS. 1A and 2A.

For example, the buffer layer 42 may also employ the implementationmethod of FIG. 1A. The surface of the buffer layer 42 includes aplurality of pores, and the pores may function as the space forsubsequent recrystallization of the silicon layer, and a partial siliconmaterial of the annealed polysilicon layer is filled into the pores. Forexample, after forming the silicon layer 43 on the buffer layer 42, themanufacturing method may further include roughening the buffer layer 42to form the pores on the surface of the buffer layer 42. The aperture issmaller than 20 nm, for example. The relevant implementation method mayrefer to the relevant description of the FIG. 1A, and detaileddescriptions thereof will be omitted.

The buffer layer 42 may also employ the implementation method of theFIG. 2A. The step of forming the buffer layer 42 includes: forming afirst sub-buffer layer on the substrate 41; and forming a secondsub-buffer layer on the first sub-buffer layer, wherein the meticulousdegree of the second sub-buffer layer is lower than that of the firstsub-buffer layer. The first sub-buffer layer may be a diffusion barrierlayer. The relevant implementation method may refer to the relevantdescription of the FIG. 2A, and detailed descriptions thereof will beomitted.

In summary, in the method of manufacturing the low temperaturepolysilicon thin film and the transistor, due to the provision of theamorphous silicon with the recrystallization growth space, the squeezebetween the crystals can be eased in the amorphous siliconrecrystallization process, and thus the sizes of the protrusions of thesurface of the polysilicon layer are significantly smaller. In thepreferred case, the aspect ratio of the protrusions is smaller than 0.3and even smaller than 0.2.

In addition, because the aspect ratios of the protrusions of the surfaceof the polysilicon layer are smaller than 0.3, the properties of theelements may be more consistent. When such a low temperature polysiliconthin film transistor is employed as a switch or driver of a displaypanel, the color uniformity of the display panel can be better.

Although the disclosure has been described with reference to specificembodiments, this description is not meant to be construed in a limitingsense. Various modifications of the disclosed embodiments, as well asalternative embodiments, will be apparent to persons skilled in the art.It is, therefore, contemplated that the appended claims will cover allmodifications that fall within the true scope of the disclosure.

What is claimed is:
 1. A method of manufacturing a low temperaturepolysilicon thin film, comprising the steps of: forming a buffer layeron a substrate; forming a silicon layer on the buffer layer; rougheninga surface of the silicon layer to form an uneven surface as arecrystallization growth space; and annealing the silicon layer to forma polysilicon layer, and a partial silicon material of the polysiliconlayer is formed on the recrystallization growth space.
 2. The methodaccording to claim 1, wherein the step of roughening the surface of thesilicon layer is to etch the surface of the silicon layer.
 3. The methodaccording to claim 1, wherein a surface of the buffer layer includes aplurality of pores, and a partial silicon material of the polysiliconlayer is filled into the pores.
 4. The method according to claim 3,wherein the step of forming the buffer layer on the substrate comprises:forming a first sub-buffer layer on the substrate; and forming a secondsub-buffer layer on the first sub-buffer layer, wherein a meticulousdegree of the second sub-buffer layer is lower than a meticulous degreeof the first sub-buffer layer.
 5. The method according to claim 4,wherein the first sub-buffer layer is a diffusion barrier layer.
 6. Themethod according to claim 3, further comprising a step of: rougheningthe buffer layer to form the pores on the surface of the buffer layerbefore forming the silicon layer on the buffer layer.
 7. The methodaccording to claim 1, further comprising steps of: providing a maskbefore the step of annealing the silicon layer to form the polysiliconlayer; and transferring a pattern from the mask to the silicon layer,wherein the pattern is left with a recrystallization growth space. 8.The method according to claim 7, wherein a portion of the transferredpattern on the silicon layer functions as a trench area, and therecrystallization growth space is located on a lateral side of theportion.
 9. The method according to claim 1, wherein the annealing islaser annealing.
 10. A method of manufacturing a low temperaturepolysilicon thin film, comprising the steps of: forming a buffer layeron a substrate; forming a silicon layer on the buffer layer; etching asurface of the silicon layer to roughen the surface of the silicon layerto form an uneven surface as a first recrystallization growth space;providing a mask; transferring a pattern from the mask to the siliconlayer, wherein the pattern is left with a second recrystallizationgrowth space, a portion of the transferred pattern on the silicon layerfunctions as a trench area, and the second recrystallization growthspace is located on a lateral side of the portion; and laser annealingthe silicon layer to form a polysilicon layer, and a partial siliconmaterial of the polysilicon layer is filled into the firstrecrystallization growth space and the second recrystallization growthspace.
 11. The method according to claim 10, wherein the step of formingthe buffer layer on the substrate comprises: forming a first sub-bufferlayer on the substrate, wherein the first sub-buffer layer is adiffusion barrier layer; forming a second sub-buffer layer on the firstsub-buffer layer, wherein a meticulous degree of the second sub-bufferlayer is lower than a meticulous degree of the first sub-buffer layer;roughening the second sub-buffer layer to form a plurality of pores onthe surface of the second sub-buffer layer; wherein the silicon layer isformed on the second sub-buffer layer; wherein a step of laser annealingthe silicon layer to form the polysilicon layer with a partial siliconmaterial of the polysilicon layer being filled into the pores, the firstrecrystallization growth space, and the second recrystallization growthspace.
 12. A method of manufacturing a low temperature polysilicon thinfilm transistor, comprising the steps of: forming a buffer layer on asubstrate; forming a silicon layer on the buffer layer; roughening asurface of the silicon layer to form an uneven surface as arecrystallization growth space; annealing the silicon layer to form apolysilicon layer, and a partial silicon material of the polysiliconlayer is formed on the recrystallization growth space; forming a gateinsulating layer on the polysilicon layer; forming a gate on the gateinsulating layer; and forming a source electrode and a drain electrode,wherein the source electrode and the drain electrode are electricallyconnected to the polysilicon layer.
 13. The method according to claim12, wherein the step of roughening the surface of the silicon layer isto etch the surface of the silicon layer.
 14. The method according toclaim 12, wherein a surface of the buffer layer includes a plurality ofpores, and a partial silicon material of the polysilicon layer is filledinto the pores.
 15. The method according to claim 14, wherein the stepof forming the buffer layer on the substrate comprises: forming a firstsub-buffer layer on the substrate; and forming a second sub-buffer layeron the first sub-buffer layer, wherein a meticulous degree of the secondsub-buffer layer is lower than a meticulous degree of the firstsub-buffer layer.
 16. The method according to claim 15, wherein thefirst sub-buffer layer is a diffusion barrier layer.
 17. The methodaccording to claim 14, further comprising a step of: roughening thebuffer layer to form the pores on the surface of the buffer layer beforeforming the silicon layer on the buffer layer.
 18. The method accordingto claim 12, further comprising steps of: providing a mask before thestep of annealing the silicon layer to form the polysilicon layer; andtransferring a pattern from the mask to the silicon layer, wherein thepattern is left with a recrystallization growth space.
 19. The methodaccording to claim 18, wherein a portion of the transferred pattern onthe silicon layer functions as a trench area, and the recrystallizationgrowth space is located on a lateral side of the portion.
 20. The methodaccording to claim 12, wherein the annealing is laser annealing.